src/org/ibex/js/Interpreter.java

   1 // Copyright 2000-2005 the Contributors, as shown in the revision logs.
   2 // Licensed under the Apache Public Source License 2.0 ("the License").
   3 // You may not use this file except in compliance with the License.
   4
   5 package org.ibex.js;
   6
   7 import org.ibex.util.*;
   8 import java.util.*;
   9
  10 /** Encapsulates a single JS interpreter (ie call stack) */
  11 class Interpreter implements ByteCodes, Tokens, Pausable {
  12     // Thread-Interpreter Mapping /////////////////////////////////////////////////////////////////////////
  13
  14     static Interpreter current() { return (Interpreter)threadToInterpreter.get(Thread.currentThread()); }
  15     private static Hashtable threadToInterpreter = new Hashtable();
  16
  17
  18     // Instance members and methods //////////////////////////////////////////////////////////////////////
  19
  20     int pausecount;               ///< the number of times pause() has been invoked; -1 indicates unpauseable
  21     JSFunction f = null;          ///< the currently-executing JSFunction
  22     JSScope scope;                ///< the current top-level scope (LIFO stack via NEWSCOPE/OLDSCOPE)
  23     final Stack stack = new Stack(); ///< the object stack
  24     int pc = 0;                   ///< the program counter
  25
  26     Interpreter(JSFunction f, boolean pauseable, JS[] args) {
  27         this.f = f;
  28         this.pausecount = pauseable ? 0 : -1;
  29         this.scope = f.parentScope;
  30         try {
  31             stack.push(new CallMarker(null));    // the "root function returned" marker -- f==null
  32             stack.push(new JSArgs(args, f)); // FIXME: temprorary bug fix
  33         } catch(JSExn e) {
  34             throw new Error("should never happen");
  35         }
  36     }
  37
  38     Interpreter(JS.Trap t, JS val, boolean pauseOnPut) {
  39         this.pausecount = -1;
  40         try {
  41             setupTrap(t,val,new TrapMarker(null,t,val,pauseOnPut));
  42         } catch(JSExn e) {
  43             throw new Error("should never happen");
  44         }
  45     }
  46
  47     private boolean get = false;
  48     // FIXME: split this stuff out into a Script instance control object
  49     //        so it's possible to make JS either single or multi threaded.
  50     /** this is the only synchronization point we need in order to be threadsafe */
  51     public synchronized Object run(Object o) throws JSExn {
  52         if (f == null) throw new AlreadyRunningException("function already finished");
  53         if (scope == null) throw new RuntimeException("scope is null");
  54
  55         Thread t = Thread.currentThread();
  56         Interpreter old = (Interpreter)threadToInterpreter.get(t);
  57         threadToInterpreter.put(t, this);
  58
  59         if (get) stack.push(o);
  60
  61         try {
  62             return run();
  63         } finally {
  64             if (old == null) threadToInterpreter.remove(t);
  65             else threadToInterpreter.put(t, old);
  66         }
  67     }
  68
  69     public void pause() throws NotPausableException {
  70         if (pausecount == -1 || f == null) throw new NotPausableException();
  71         pausecount++;
  72         switch(f.op[pc]) {
  73             case Tokens.RETURN: case ByteCodes.PUT: get = false; break;
  74             case ByteCodes.GET: case ByteCodes.GET_PRESERVE: case ByteCodes.CALLMETHOD: case ByteCodes.CALL: get = true; break;
  75             default: throw new Error("paused on unexpected bytecode: " + f.op[pc]);
  76         }
  77     }
  78
  79     static int getLine() {
  80         Interpreter c = Interpreter.current();
  81         return c == null || c.f == null || c.pc < 0 || c.pc >= c.f.size ? -1 : c.f.line[c.pc];
  82     }
  83
  84     static String getSourceName() {
  85         Interpreter c = Interpreter.current();
  86         return c == null || c.f == null ? null : c.f.sourceName;
  87     }
  88
  89     private static JSExn je(String s) { return new JSExn(getSourceName() + ":" + getLine() + " " + s); }
  90
  91     private JS run() throws JSExn {
  92
  93         // if pausecount changes after a get/put/call, we know we've been paused
  94         final int initialPauseCount = pausecount;
  95
  96         OUTER: for(;; pc++) {
  97         try {
  98             int op = f.op[pc];
  99             Object arg = f.arg[pc];
 100             if(op == FINALLY_DONE) {
 101                 FinallyData fd = (FinallyData) stack.pop();
 102                 if(fd == null) continue OUTER; // NOP
 103                 if(fd.exn != null) throw fd.exn;
 104                 op = fd.op;
 105                 arg = fd.arg;
 106             }
 107             switch(op) {
 108             case LITERAL: stack.push((JS)arg); break;
 109             case OBJECT: stack.push(new JS.Obj()); break;
 110             case ARRAY: stack.push(new JSArray(JSU.toInt((JS)arg))); break;
 111             //case DECLARE: scope.declare((JS)(arg==null ? stack.peek() : arg)); if(arg != null) stack.push((JS)arg); break;
 112             case JT: if (JSU.toBoolean((JS)stack.pop())) pc += JSU.toInt((JS)arg) - 1; break;
 113             case JF: if (!JSU.toBoolean((JS)stack.pop())) pc += JSU.toInt((JS)arg) - 1; break;
 114             case JMP: pc += JSU.toInt((JS)arg) - 1; break;
 115             case POP: stack.pop(); break;
 116             case SWAP: stack.swap(); break;
 117             case DUP: stack.push(stack.peek()); break;
 118             case NEWSCOPE: {
 119                 int n = JSU.toInt((JS)arg);
 120                 scope = new JSScope(scope,(n>>>16)&0xffff,(n>>>0)&0xffff);
 121                 break;
 122             }
 123             case OLDSCOPE: scope = scope.parent; break;
 124             case GLOBALSCOPE: stack.push(scope.getGlobal()); break;
 125             case SCOPEGET: stack.push(scope.get((JS)arg)); break;
 126             case SCOPEPUT: {
 127                 // FIXME: HACK: share this around more and find the callee.
 128                 Object val = stack.peek();
 129                 if (val != null && val instanceof JS[]) val = new JSArgs((JS[])val, null);
 130                 scope.put((JS)arg, (JS)val); break;
 131             }
 132             case ASSERT: if (!JSU.toBoolean((JS)stack.pop())) throw je("ibex.assertion.failed"); break;
 133             case BITNOT: stack.push(JSU.N(~JSU.toLong((JS)stack.pop()))); break;
 134             case BANG: stack.push(JSU.B(!JSU.toBoolean((JS)stack.pop()))); break;
 135             case NEWFUNCTION: stack.push(((JSFunction)arg)._cloneWithNewParentScope(scope)); break;
 136             case LABEL: break;
 137
 138             case TYPEOF: {
 139                 Object o = stack.pop();
 140                 if (o == null) stack.push(null);
 141                 else if (o instanceof JSString) stack.push(JSU.S("string"));
 142                 else if (o instanceof JSNumber.B) stack.push(JSU.S("boolean"));
 143                 else if (o instanceof JSNumber) stack.push(JSU.S("number"));
 144                 else stack.push(JSU.S("object"));
 145                 break;
 146             }
 147
 148             case PUSHKEYS: {
 149                 JS o = (JS)stack.peek();
 150                 stack.push(o == null ? null : o.keys());
 151                 break;
 152             }
 153
 154             case LOOP:
 155                 stack.push(new LoopMarker(pc, (String)(pc > 0 && f.op[pc - 1] == LABEL ? f.arg[pc - 1] : null), scope));
 156                 stack.push(JSU.T);
 157                 break;
 158
 159             case BREAK:
 160             case CONTINUE:
 161                 while(!stack.empty()) {
 162                     Object o = stack.pop();
 163                     if (o instanceof CallMarker) je("break or continue not within a loop");
 164                     if (o instanceof TryMarker) {
 165                         if(((TryMarker)o).finallyLoc < 0) continue; // no finally block, keep going
 166                         stack.push(new FinallyData(op, arg));
 167                         scope = ((TryMarker)o).scope;
 168                         pc = ((TryMarker)o).finallyLoc - 1;
 169                         continue OUTER;
 170                     }
 171                     if (o instanceof LoopMarker) {
 172                         if (arg == null || arg.equals(((LoopMarker)o).label)) {
 173                             int loopInstructionLocation = ((LoopMarker)o).location;
 174                             int endOfLoop = JSU.toInt((JS)f.arg[loopInstructionLocation]) + loopInstructionLocation;
 175                             scope = ((LoopMarker)o).scope;
 176                             if (op == CONTINUE) { stack.push(o); stack.push(JSU.F); }
 177                             pc = op == BREAK ? endOfLoop - 1 : loopInstructionLocation;
 178                             continue OUTER;
 179                         }
 180                     }
 181                 }
 182                 throw new Error("CONTINUE/BREAK invoked but couldn't find LoopMarker at " +
 183                                 getSourceName() + ":" + getLine());
 184
 185             case TRY: {
 186                 int[] jmps = (int[]) arg;
 187                 // jmps[0] is how far away the catch block is, jmps[1] is how far away the finally block is
 188                 // each can be < 0 if the specified block does not exist
 189                 stack.push(new TryMarker(jmps[0] < 0 ? -1 : pc + jmps[0], jmps[1] < 0 ? -1 : pc + jmps[1], this));
 190                 break;
 191             }
 192
 193             case RETURN: {
 194                 JS retval = (JS)stack.pop();
 195                 while(!stack.empty()) {
 196                     Object o = stack.pop();
 197                     if (o instanceof TryMarker) {
 198                         if(((TryMarker)o).finallyLoc < 0) continue;
 199                         stack.push(retval);
 200                         stack.push(new FinallyData(RETURN));
 201                         scope = ((TryMarker)o).scope;
 202                         pc = ((TryMarker)o).finallyLoc - 1;
 203                         continue OUTER;
 204                     } else if (o instanceof CallMarker) {
 205                         boolean didTrapPut = false;
 206                         if (o instanceof TrapMarker) { // handles return component of a write trap
 207                             TrapMarker tm = (TrapMarker) o;
 208                             boolean cascade = tm.t.isWriteTrap() && !tm.cascadeHappened && !JSU.toBoolean(retval);
 209                             if(cascade) {
 210                                 JS.Trap t = tm.t.nextWrite();
 211                                 if(t == null && tm.t.target() instanceof JS.Clone) {
 212                                     t = ((JS.Clone)tm.t.target()).clonee.getTrap(tm.t.key());
 213                                     if(t != null && !t.isWriteTrap()) t = t.nextWrite();
 214                                 }
 215                                 if(t != null) {
 216                                     tm.t = t; // we reuse the old trap marker
 217                                     setupTrap(t, tm.val, tm);
 218                                     pc--; // we increment it on the next iter
 219                                     continue OUTER;
 220                                 } else {
 221                                     didTrapPut = true;
 222                                     if(!tm.pauseOnPut) tm.t.target().put(tm.t.key(), tm.val);
 223                                 }
 224                             }
 225                         }
 226                         CallMarker cm = (CallMarker) o;
 227                         scope = cm.scope;
 228                         pc = cm.pc - 1;
 229                         f = cm.f;
 230                         if (didTrapPut) {
 231                             if (((TrapMarker)cm).pauseOnPut) { pc++; return ((TrapMarker)cm).val; }
 232                             if (pausecount > initialPauseCount) { pc++; return null; }   // we were paused
 233                         } else {
 234                             stack.push(retval);
 235                         }
 236                         if (f == null) return retval;
 237                         continue OUTER;
 238                     }
 239                 }
 240                 throw new Error("error: RETURN invoked but couldn't find a CallMarker!");
 241             }
 242
 243             case CASCADE: {
 244                 boolean write = JSU.toBoolean((JS)arg);
 245                 JS val = write ? (JS)stack.pop() : null;
 246                 CallMarker o = stack.findCall();
 247                 if(!(o instanceof TrapMarker)) throw new JSExn("tried to CASCADE while not in a trap");
 248                 TrapMarker tm = (TrapMarker) o;
 249                 JS key = tm.t.key();
 250                 JS target = tm.t.target();
 251                 if(tm.t.isWriteTrap() != write)
 252                     throw new JSExn("tried to do a "+(write?"write":"read") + " cascade in a " + (write?"read":"write") + " trap");
 253                 JS.Trap t = write ? tm.t.nextWrite() : tm.t.nextRead();
 254                 while (t == null && target instanceof JS.Clone) {
 255                     target = ((JS.Clone)target).clonee;
 256                     t = target.getTrap(key);
 257                     if(t != null) t = write ? t.write() : t.read();
 258                 }
 259                 if(write) {
 260                     tm.cascadeHappened = true;
 261                     stack.push(val);
 262                 }
 263                 if(t != null) {
 264                     setupTrap(t,val,new TrapMarker(this,t,val,tm.pauseOnPut));
 265                     pc--; // we increment later
 266                 } else {
 267                     if(write) {
 268                         if (tm.pauseOnPut) { pc++; return val; }
 269                         target.put(key,val);
 270                     } else {
 271                         JS ret = target.get(key);
 272                         if (ret != null && ret instanceof JS.Method) ret = new Stub(target, key);
 273                         stack.push(ret);
 274                     }
 275                     if (pausecount > initialPauseCount) { pc++; return null; }   // we were paused
 276                 }
 277                 break;
 278             }
 279
 280             case PUT: {
 281                 JS val = (JS)stack.pop();
 282                 JS key = (JS)stack.pop();
 283                 JS target = (JS)stack.peek();
 284                 if (target == null) throw je("tried to put " + JSU.str(val) + " to the " + JSU.str(key) + " property on the null value");
 285                 if (key == null) throw je("tried to assign \"" + JSU.str(val) + "\" to the null key");
 286
 287                 JS.Trap t = target.getTrap(key);
 288                 if(t != null) t = t.write();
 289
 290                 if(t == null && target instanceof JS.Clone) {
 291                     target = ((JS.Clone)target).clonee;
 292                     t = target.getTrap(key);
 293                     if(t != null) t = t.nextWrite();
 294                 }
 295
 296                 stack.push(val);
 297
 298                 if(t != null) {
 299                     setupTrap(t,val,new TrapMarker(this,t,val));
 300                     pc--; // we increment later
 301                 } else {
 302                     target.put(key,val);
 303                     if (pausecount > initialPauseCount) { pc++; return null; }   // we were paused
 304                 }
 305                 break;
 306             }
 307
 308             case GET:
 309             case GET_PRESERVE: {
 310                 JS target, key;
 311                 if (op == GET) {
 312                     key = arg == null ? (JS)stack.pop() : (JS)arg;
 313                     target = (JS)stack.pop();
 314                 } else {
 315                     key = (JS)stack.pop();
 316                     target = (JS)stack.peek();
 317                     stack.push(key);
 318                 }
 319                 JS ret = null;
 320                 if (key == null) throw je("tried to get the null key from " + JSU.str(target));
 321                 if (target == null) throw je("tried to get property \"" + JSU.str(key) + "\" from the null object");
 322
 323                 JS.Trap t = null;
 324                 try { t = target.getTrap(key); } catch (JSExn e) {}
 325                 if(t != null) t = t.read();
 326
 327                 if(t == null && target instanceof JS.Clone) {
 328                     target = ((JS.Clone)target).clonee;
 329                     t = target.getTrap(key);
 330                     if(t != null) t = t.nextRead();
 331                 }
 332
 333                 if(t != null) {
 334                     setupTrap(t,null,new TrapMarker(this,t,null));
 335                     pc--; // we increment later
 336                 } else {
 337                     ret = target.get(key);
 338                     if (pausecount > initialPauseCount) { pc++; return null; }   // we were paused
 339
 340                     if (ret != null && ret instanceof JS.Method) ret = new Stub(target, key);
 341                     stack.push(ret);
 342                 }
 343                 break;
 344             }
 345
 346             case CALL: case CALLMETHOD: {
 347                 JS[] jsargs;
 348                 if (arg instanceof JSNumber.I) {
 349                     // FIXME: we should be able to recycle JS[]'s here
 350                     jsargs = new JS[((JSNumber.I)arg).toInt()];
 351                     for (int i=0; i < jsargs.length; i++) jsargs[i] = (JS)stack.pop();
 352                 } else jsargs = (JS[])arg;
 353
 354                 JS method = null;
 355                 JS ret = null;
 356                 JS object = (JS)stack.pop();
 357
 358                 if (op == CALLMETHOD) {
 359                     if (object == null) {
 360                         method = (JS)stack.pop();
 361                         object = (JS)stack.pop();
 362                         throw new JSExn("function '"+JSU.str(method)+"' not found in " + object.getClass().getName());
 363                     } else if (object instanceof JS.Method) {
 364                         method = (JS)stack.pop();
 365                         object = (JS)stack.pop();
 366                     } else {
 367                         stack.pop();
 368                         stack.pop();
 369                     }
 370                 }
 371
 372                 if (object instanceof JSFunction) {
 373                     stack.push(new CallMarker(this));
 374                     f = (JSFunction)object;
 375                     stack.push(new JSArgs(jsargs, f));
 376                     scope = f.parentScope;
 377                     pc = -1;
 378                     break;
 379                 } else {
 380                     JS c = (JS)object;
 381                     ret = c.call(method, jsargs);
 382                 }
 383
 384                 if (pausecount > initialPauseCount) { pc++; return null; }
 385                 stack.push(ret);
 386                 break;
 387             }
 388
 389             case THROW:
 390                 throw new JSExn((JS)stack.pop(), this);
 391
 392             case ADD_TRAP: case DEL_TRAP: {
 393                 JS val = (JS)stack.pop();
 394                 JS key = (JS)stack.pop();
 395                 JS js = (JS)stack.peek();
 396                 // A trap addition/removal
 397                 if(!(val instanceof JSFunction)) throw new JSExn("tried to add/remove a non-function trap");
 398                 if(op == ADD_TRAP) js.addTrap(key, val);
 399                 else js.delTrap(key, val);
 400                 break;
 401             }
 402
 403             case ADD: {
 404                 int count = ((JSNumber)arg).toInt();
 405                 if(count < 2) throw new Error("this should never happen");
 406                 if(count == 2) {
 407                     // common case
 408                     JS right = (JS)stack.pop();
 409                     JS left = (JS)stack.pop();
 410                     JS ret;
 411                     if(left instanceof JSString || right instanceof JSString)
 412                         ret = JSU.S(JSU.toString(left).concat(JSU.toString(right)));
 413                     else if(left instanceof JSNumber.D || right instanceof JSNumber.D)
 414                         ret = JSU.N(JSU.toDouble(left) + JSU.toDouble(right));
 415                     else {
 416                         long l = JSU.toLong(left) + JSU.toLong(right);
 417                         if(l < Integer.MIN_VALUE || l > Integer.MAX_VALUE) ret = JSU.N(l);
 418                         ret = JSU.N((int)l);
 419                     }
 420                     stack.push(ret);
 421                 } else {
 422                     JS[] args = new JS[count];
 423                     while(--count >= 0) args[count] = (JS)stack.pop();
 424                     if(args[0] instanceof JSString) {
 425                         StringBuffer sb = new StringBuffer(64);
 426                         for(int i=0;i<args.length;i++) sb.append(JSU.toString(args[i]));
 427                         stack.push(JSU.S(sb.toString()));
 428                     } else {
 429                         int numStrings = 0;
 430                         for(int i=0;i<args.length;i++) if(args[i] instanceof JSString) numStrings++;
 431                         if(numStrings == 0) {
 432                             double d = 0.0;
 433                             for(int i=0;i<args.length;i++) d += JSU.toDouble(args[i]);
 434                             stack.push(JSU.N(d));
 435                         } else {
 436                             int i=0;
 437                             StringBuffer sb = new StringBuffer(64);
 438                             if(!(args[0] instanceof JSString || args[1] instanceof JSString)) {
 439                                 double d=0.0;
 440                                 do {
 441                                     d += JSU.toDouble(args[i++]);
 442                                 } while(!(args[i] instanceof JSString));
 443                                 sb.append(JSU.toString(JSU.N(d)));
 444                             }
 445                             while(i < args.length) sb.append(JSU.toString(args[i++]));
 446                             stack.push(JSU.S(sb.toString()));
 447                         }
 448                     }
 449                 }
 450                 break;
 451             }
 452
 453             default: {
 454                 JS right = (JS)stack.pop();
 455                 JS left = (JS)stack.pop();
 456                 switch(op) {
 457
 458                 case BITOR: stack.push(JSU.N(JSU.toLong(left) | JSU.toLong(right))); break;
 459                 case BITXOR: stack.push(JSU.N(JSU.toLong(left) ^ JSU.toLong(right))); break;
 460                 case BITAND: stack.push(JSU.N(JSU.toLong(left) & JSU.toLong(right))); break;
 461
 462                 case SUB: stack.push(JSU.N(JSU.toDouble(left) - JSU.toDouble(right))); break;
 463                 case MUL: stack.push(JSU.N(JSU.toDouble(left) * JSU.toDouble(right))); break;
 464                 case DIV: stack.push(JSU.N(JSU.toDouble(left) / JSU.toDouble(right))); break;
 465                 case MOD: stack.push(JSU.N(JSU.toDouble(left) % JSU.toDouble(right))); break;
 466
 467                 case LSH: stack.push(JSU.N(JSU.toLong(left) << JSU.toLong(right))); break;
 468                 case RSH: stack.push(JSU.N(JSU.toLong(left) >> JSU.toLong(right))); break;
 469                 case URSH: stack.push(JSU.N(JSU.toLong(left) >>> JSU.toLong(right))); break;
 470
 471                 //#repeat </<=/>/>= LT/LE/GT/GE
 472                 case LT: {
 473                     if(left instanceof JSString && right instanceof JSString)
 474                         stack.push(JSU.B(JSU.toString(left).compareTo(JSU.toString(right)) < 0));
 475                     else
 476                         stack.push(JSU.B(JSU.toDouble(left) < JSU.toDouble(right)));
 477                 }
 478                 //#end
 479
 480                 case EQ:
 481                 case NE: {
 482                     boolean ret;
 483                     if(left == null && right == null) ret = true;
 484                     else if(left == null || right == null) ret = false;
 485                     else ret = left.equals(right);
 486                     stack.push(JSU.B(op == EQ ? ret : !ret)); break;
 487                 }
 488
 489                 default: throw new Error("unknown opcode " + op);
 490                 } }
 491             }
 492
 493         } catch(JSExn e) {
 494             catchException(e);
 495             pc--; // it'll get incremented on the next iteration
 496         } // end try/catch
 497         } // end for
 498     }
 499
 500     /** tries to find a handler withing the call chain for this exception
 501         if a handler is found the interpreter is setup to call the exception handler
 502         if a handler is not found the exception is thrown
 503     */
 504     void catchException(JSExn e) throws JSExn {
 505         while(!stack.empty()) {
 506             Object o = stack.pop();
 507             if (o instanceof CatchMarker || o instanceof TryMarker) {
 508                 boolean inCatch = o instanceof CatchMarker;
 509                 if(inCatch) {
 510                     o = (JS)stack.pop();
 511                     if(((TryMarker)o).finallyLoc < 0) continue; // no finally block, keep going
 512                 }
 513                 if(!inCatch && ((TryMarker)o).catchLoc >= 0) {
 514                     // run the catch block, this will implicitly run the finally block, if it exists
 515                     stack.push(o);
 516                     stack.push(catchMarker);
 517                     stack.push(e.getObject());
 518                     f = ((TryMarker)o).f;
 519                     scope = ((TryMarker)o).scope;
 520                     pc = ((TryMarker)o).catchLoc;
 521                     return;
 522                 } else {
 523                     stack.push(new FinallyData(e));
 524                     f = ((TryMarker)o).f;
 525                     scope = ((TryMarker)o).scope;
 526                     pc = ((TryMarker)o).finallyLoc;
 527                     return;
 528                 }
 529             }
 530         }
 531         throw e;
 532     }
 533
 534     void setupTrap(JS.Trap t, JS val, CallMarker cm) throws JSExn {
 535         stack.push(cm);
 536         stack.push(new TrapArgs(t, val));
 537         f = (JSFunction)t.function();
 538         scope = f.parentScope;
 539         pc = 0;
 540     }
 541
 542
 543     // Markers //////////////////////////////////////////////////////////////////////
 544
 545     static class Marker {}
 546
 547     static class CallMarker extends Marker {
 548         final int pc;
 549         final JSScope scope;
 550         final JSFunction f;
 551         public CallMarker(Interpreter cx) {
 552             pc = cx == null ? -1 : cx.pc + 1;
 553             scope = cx == null ? null : cx.scope;
 554             f = cx == null ? null : cx.f;
 555         }
 556     }
 557
 558     static class TrapMarker extends CallMarker {
 559         JS.Trap t;
 560         JS val;
 561         boolean cascadeHappened;
 562         final boolean pauseOnPut;
 563         public TrapMarker(Interpreter cx, JS.Trap t, JS val) { this(cx,t,val,false); }
 564         public TrapMarker(Interpreter cx, JS.Trap t, JS val, boolean pauseOnPut) {
 565             super(cx);
 566             this.t = t;
 567             this.val = val;
 568             this.pauseOnPut = pauseOnPut;
 569         }
 570     }
 571
 572     static class CatchMarker extends Marker { }
 573     private static final CatchMarker catchMarker = new CatchMarker();
 574
 575     static class LoopMarker extends Marker {
 576         final public int location;
 577         final public String label;
 578         final public JSScope scope;
 579         public LoopMarker(int location, String label, JSScope scope) {
 580             this.location = location;
 581             this.label = label;
 582             this.scope = scope;
 583         }
 584     }
 585     static class TryMarker extends Marker {
 586         final public int catchLoc;
 587         final public int finallyLoc;
 588         final public JSScope scope;
 589         final public JSFunction f;
 590         public TryMarker(int catchLoc, int finallyLoc, Interpreter cx) {
 591             this.catchLoc = catchLoc;
 592             this.finallyLoc = finallyLoc;
 593             this.scope = cx.scope;
 594             this.f = cx.f;
 595         }
 596     }
 597     static class FinallyData extends Marker {
 598         final public int op;
 599         final public Object arg;
 600         final public JSExn exn;
 601         public FinallyData(int op) { this(op,null); }
 602         public FinallyData(int op, Object arg) { this.op = op; this.arg = arg; this.exn = null; }
 603         public FinallyData(JSExn exn) { this.exn = exn; this.op = -1; this.arg = null; } // Just throw this exn
 604     }
 605
 606     static class JSArgs extends JS.Immutable {
 607         private final JS[] args;
 608         private final JS callee;
 609
 610         public JSArgs(JS[] args, JS callee) { this.args = args; this.callee = callee; }
 611
 612         public JS get(JS key) throws JSExn {
 613             if(JSU.isInt(key)) {
 614                 int i = JSU.toInt(key);
 615                 return i>=args.length ? null : args[i];
 616             }
 617             //#switch(JSU.toString(key))
 618             case "callee": return callee;
 619             case "length": return JSU.N(args.length);
 620             //#end
 621             return super.get(key);
 622         }
 623     }
 624
 625     static class TrapArgs extends JS.Immutable {
 626         private Trap t;
 627         private JS val;
 628         public TrapArgs(Trap t, JS val) { this.t = t; this.val = val; }
 629         public JS get(JS key) throws JSExn {
 630             if(JSU.isInt(key) && JSU.toInt(key) == 0) return val;
 631             //#switch(JSU.str(key))
 632             case "trapee": return t.target();
 633             case "callee": return t.function();
 634             case "trapname": return t.key();
 635             case "length": return t.isWriteTrap() ? JSU.ONE : JSU.ZERO;
 636             //#end
 637             return super.get(key);
 638         }
 639     }
 640
 641     static class Stub extends JS.Immutable {
 642         private JS method;
 643         JS obj;
 644         public Stub(JS obj, JS method) { this.obj = obj; this.method = method; }
 645         public JS call(JS method, JS[] args) throws JSExn {
 646             if (method==null) return obj.call(this.method, args);
 647             return super.call(method, args);
 648         }
 649     }
 650
 651     static final class Stack {
 652         private static final int MAX_STACK_SIZE = 512;
 653         private Object[] stack = new Object[8];
 654         private int sp = 0;
 655
 656         boolean empty() { return sp == 0; }
 657         void push(Object o) throws JSExn { if(sp == stack.length) grow(); stack[sp++] = o; }
 658         Object peek() { if(sp == 0) throw new RuntimeException("stack underflow"); return stack[sp-1]; }
 659         final Object pop() { if(sp == 0) throw new RuntimeException("stack underflow"); return stack[--sp]; }
 660         void swap() throws JSExn {
 661             if(sp < 2) throw new JSExn("stack overflow");
 662             Object tmp = stack[sp-2];
 663             stack[sp-2] = stack[sp-1];
 664             stack[sp-1] = tmp;
 665         }
 666         CallMarker findCall() {
 667             for(int i=sp-1;i>=0;i--) if(stack[i] instanceof CallMarker) return (CallMarker) stack[i];
 668             return null;
 669         }
 670         void grow() throws JSExn {
 671             if(stack.length >= MAX_STACK_SIZE) throw new JSExn("stack overflow");
 672             Object[] stack2 = new Object[stack.length * 2];
 673             System.arraycopy(stack,0,stack2,0,stack.length);
 674             stack = stack2;
 675         }
 676
 677         void backtrace(JSExn e) {
 678             for(int i=sp-1;i>=0;i--) {
 679                 if (stack[i] instanceof CallMarker) {
 680                     CallMarker cm = (CallMarker)stack[i];
 681                     if(cm.f == null) break;
 682                     String s = cm.f.sourceName + ":" + cm.f.line[cm.pc-1];
 683                     if(cm instanceof Interpreter.TrapMarker)
 684                         s += " (trap on " + JSU.str(((Interpreter.TrapMarker)cm).t.key()) + ")";
 685                     e.addBacktrace(s);
 686                 }
 687             }
 688         }
 689     }
 690 }